This invention relates to a shield for an ignition device, particularly a shield for a gas pilot used to ignite a gas burner. Use of the shield extends the useful life of the pilot and reduces gas stove maintenance.
Gas burners, especially on cook stoves, are used intermittently. The supply of gas to such a burner can be completely shut off by the operator to extinguish the burner. When a pilot flame is located near the burner, reapplication of the supply of gas to the burner is sufficient to reignite the burner. Thus, intermittent operation of the burner is made possible by directing a continuously lit pilot jet toward the burner. When the pilot is misaligned or extinguished, intermittent operation of the burner is not possible and there is an increased risk of unexpected combustion and explosion. Accidental misalignment and extinguishment of the pilot can arise in several ways.
Accidental misalignment of the pilot in relation to the burner occurs when the operator carelessly allows a heavy object to strike the pilot. For example, if the burner is used for heating materials in a vessel, the pilot can be misaligned, damaged, or extinguished when the vessel comes in contact with the pilot. The vessel is usually separated from the burner by a grate so that the vessel is heated by a cushion of air rather than by the flames from the burner. The pilot can be misaligned, damaged, or extinguished when the grate is allowed to strike the pilot. Proper cleaning of commercial cook stoves often requires the frequent removal and replacement of the grate, consequently increasing the risk of harmful contact between the grate and the pilot.
Accidental extinguishment of the pilot can occur suddenly or over the course of time. Sudden changes in the air flowing around the pilot can extinguish the pilot. For example, when an exhaust hood which is operated over the burner is turned on or off, the sudden change in air flow can extinguish the pilot. When materials that spatter are heated over the burner, the spattered particles and droplets can enter the orifices of the pilot and suddenly extinguish the pilot, or burn and leave deposits that eventually foul an orifice, rendering the pilot inefficient or unable to ignite the burner. During maintenance of the burner, cleaning solutions can enter an orifice in the pilot and later form deposits within the pilot that obstruct and extinguish it. Removal of deposits is often more difficult than replacement of the pilot and its gas feeder tube. Replacement of the pilot necessarily interrupts commercial use of the burner and is costly in labor and materials.
Operation of the pilot near the burner can interfere with use of the burner to provide even heating. Because the pilot flame is directed toward the burner for ignition, the heat of the flame can create a hot spot on the vessel located over the burner. Undesirable uneven heating of the vessel and its contents results.
Covers for pilot jets have been disclosed in the prior art. Typical of such devices are those wherein the cover is used to sense heat or to conduct heat to a sensing device. The sensing device usually acts to shut off the supply of gas to the pilot and the burner to prevent gas from escaping from an extinguished pilot or burner. In this art, the size and orientation of the cover is not sufficient to protect the pilot from being extinguished.
Another implementation of a pilot igniter and gas burner in the prior art is adapted for use as an oven burner in a gas cooking range. The typical implementation uses a constant first pilot from a range top burner in communication with a flash tube to ignite a second pilot near the oven burner supplied with gas only when the oven burner is to be used. A sudden change in air flow caused by opening or closing the oven door may extinguish the second pilot which is then relit by the first pilot via the flash tube. In such an implementation, the second pilot is not protected from being extinguished by draft or obstruction.
To help prevent extinguishment of a pilot due to drafts, including the draft caused by the sudden ignition of a burner, pilots have been disclosed wherein an orifice in the pilot is formed as a slot rather than as a circular hole. Such a pilot typically consumes more fuel than a pilot having a circular orifice. In one implementation, the fuel supply to the pilot is maintained at a low standby level until ignition of the burner is desired, whereupon the gas supply to the slotted pilot is increased prior to supplying gas to the burner. In many applications, a slotted pilot would consume fuel at a cost that outweighs the convenience and simplicity of a continuous standing pilot.
In place of a continuous pilot, an electrostatic igniter has been used to ignite a gas burner for a gas barbecue grill. In the typical arrangement, a high voltage cable is terminated in the vicinity of a ground conductor so that a spark between the termination and the conductor ignites gas escaping from the burner. Operation of the igniter depends upon maintaining proper position of the igniter in relation to the burner and also upon maintaining the cleanliness of the termination and conductor in spite of grease drippings and other deposits incident to barbecuing. In one implementation, an igniter enclosure includes means to hold the high voltage wire within the enclosure and in juxtaposition to one wall of the enclosure. The wall of the enclosure serves as the ground conductor. In another implementation, a similar igniter enclosure is shown with adjustable means for maintaining the position of the housing in relation to the burner. Such implementations do not provide the structural integrity required for a commercial cook stove or the like. And, although the termination and one wall of the enclosure are protected from deposits that interfere with ignition, deposits can collect within the igniter enclosure on surfaces that are not accessible for cleaning to meet standards for cleanliness that apply to commercial cook stoves and the like.
Thus, there remains a need for a simple device that protects a gas pilot igniter in a manner suitable for use on commercial cook stoves and the like.